Secret-signaling system



Patented Dec. 23,1919.-

H'. w. NICHOLS.

SECRET SIGNALING SYSTEM.

APPLICATION FILED SEPT II. I9l5.

QN W w M. m #0 m ,W lJTh W/fnesses:

' UNITED STATES PATENT OFFICE.

HAROLD WILLIAM NICHOLS, OF MAPLEWOOD, NEW JERSEY, ASSIGNOR, BY MESNEASSIGNMENTS, TO WESTERN ELECTRIC COMPANY, INCORPORATED, A CORPORA-' TIONOF NEW YORK.

SECRET-SIGNALING SYSTEM.

Specification of Letters Patent. Patented De 23, 1919 Application filedSeptember 11, 1915. Serial No. 50,150.

To all whom it may concern:

Be it known that I; HAROLD WILLIAM NICHOLS, a citizen of the UnitedStates, residing at Maplewood, in the county of Essex and State of NewJersey, have invented certain new and useful Improvements in Secret-Signaling Systems, of which the followlng is a full, clear, concise, andexact description.

This invention relates to a method of and apparatus for secrettransmission of intelligence.

Its object is to'transmit signals which shall be intelligible only at aproperly equipped receiving station.

A further object is tomake possible continuous transmission suitable forcommercial telephony, that is, transmission in which there is noappreciable time interval between the production of a signal and itstransmission to the receiving station.

A fundamental requirement of commercial telephony is that there shall beno delay in the transmission of signals, that is, a.

signal must be transmitted immediately upon its production. Thisrequirement precludes the use of code sending as ordinarily understood,because such sending would necessarily introduce a delay equal to thetime required for translation to code; stated in other words, thisrequirement means that there must be no storage of signals.

In order to accomplish these objects, this invention proposes to sodistort the signal transmitted from the sending station that it shall beunrecognizable in the interval between transmitting and receivingstation, to receive the signal, and, by means of supplementary modifyingapparatus at the receiving station, to restore the orlglnal character ofthe signal and finally to translate it in a suitable manner. Afundamental condition for this kind of distortion is that the order ofelectrical states which make up the signals shall not be changed,although the intervals elapsing between successive states may be changedin any arbitrary manner. If this condition is not fulfilled the resultwill be either delay in the transmission of the signal or elsesuperposition of one part of the signal upon another part, making theresultant message unintelligible.

The nature of this invention will be clear by reference to the drawing,which shows thls invention as applied to radiotelephony. In thisarrangement signals are produced by the telephone transmitter, distortedby the apparatus intervening between the transmitter and antenna,transmitted to a receiving station, received and restored to theiroriginal forms, and finally translated to audible sounds by thetelephone receiver. Referring to the drawing, 1 represents an iron wireor tape driven by the rotatable elements 2, 3 is an electro-magnet whichis energized by means of the battery 5, and mlcrophone 4, in circuitwith battery 5 and magnet 3, serves to vary the current through themagnet in accordance with speech vibrations. The result of impressingspeech vibrations upon the microphone is to alter the magnetic state ofthe wire 1, as in the magnetic detector or telegraphone, thesevariations in magnetic state being permanent and carried along withithewire' or less faithful copy of the current, in mag net 3. The magnet 6is rigidly connected to the arm 17 which passes through guides and isdriven by the cam mechanism 8. This cam may be driven by a separatesource of power, or the same source of driving power may be used for thecam and for the driving pulleys 2. The purpose of this cam-driven magnet6 is to so alter the wave form of vibrations induced in it, with respectto those produced in 3, as to be unrecognizable when transmitted fromthe antenna as explained later.

It will be obvious that if the motion of the wire 1 is uniform and ifthe magnets 3 and 6 are relatively at rest, the signal induced in 6 willbe practically an exact copy of that produced by the microphone. On theother and, if there is relative motion of-magnets 3 and 6, it is obviousthat the signal induced in 6 will be distorted, as the time phaserelation between succeeding portions of the signal wave will bemodified. The object of this device is to so distort the signal that itwill be unintelligible except by a properly equipped receiving station.In designing and operating this cam-driven mechanism, it is essentialthat the relative speed of mag nets 3 and 6 shall never be great enoughto cause superposition of different parts of the message. In order toefi'ace the record of the signal, after it is communicated to 6, and toplace the wire 1 in a condition suitable for the recording of a newmessage, the permanent magnet 9 is placed below the tape, as shown inthe figure. Transformer 10 serves to impress the vibrations in magnet 6upon the input circuit of a thermionic element 11 of the audion type. Bymeans of transformer 13, oscillations of power value, comparable withthose produced in 6, are impressed upon the same input circuit by meansof the alternating current generator 12. In this figure this is shown asa thermionic oscillator having its input circuit connected with itsoutput circuit. This particular arrangement is the invention of Ralph V.L. Hartley, for improvement in oscillation generators, filed June ,1,1915, Serial No. 31,476. It is obvious, however, that another type ofalternatingcurrent generator may also be used. 14 is a battery placed inthe input circuit of the thermionic element and 15 another battery inits output circuit. In order to obtain effective modulation, it isdesirable to operate the thermionic device 11 over a range of impressedelectromotive forces throughout which the curvature of itscharacteristic curve is large. Battery 14 serves to impress upon theinput circuit an initial electromotive force corre sponding to a pointin this range. The thermionic element 11, therefore, serves, inconnection with magnet 6 and the oscillation generator 12, as a devicefor producing in its output circuit modulated high frequencyoscillations. This modulating scheme is the invention of Van der Bijland is described and claimed in his application for radiocommunication,Serial No. 46,643, filed Air gust 21, 1915. By means of transformer 16,these oscillations are transferred to the tuned circuit comprising onewinding of 16 and the condenser 17. Across the terminals of 17 is placeda group of amplifiers 18 arranged in parallel. The function of battery19 is similar to that of 14, and that of battery 20 to that of battery15, except that in the case of the amplifier the potentials of thesebatteries are so adjusted as to cause the amplifier to operate over thestraight line portion of the characteristic curve. These amplifiers,therefore, produce a'ugmented modulated high frequency oscillations inthe output circuit. By means of transformer 21, these oscillations aretransferred to the sending antenna 22 through which electromagneticWaves in the other are orlgmated.

- the same direction as the tape, greater than the speed of the tape.Except 130 These waves impinge upon antenna 23 of the receiving stationand are transferred, by means of transformer 24, to a tuned circuitcontaining condenser 25. The amplifier 26 increases the energy ofoscillations in this tuned circuit, and this increased energy, by meansof transformer 29, is transferred to the input circuit of a thermionicelement 33. 27 and 28 are batteries for use in connection with theamplifier. The condenser 30 performs the same function as condenser 25.In the grid circuit of element 33 is placed condenser 31 shunted by theresistance 32. The function of element 33 is to detect the incoming highfrequency modulated oscillations with the result that only the envelopof the oscillations appears in its output circuit. Battery 34 suppliesthe direct current necessary for this output circuit. Transformer 35serves to transfer the power from the output circuit of element 33 tothe receiving magnet 36. This magnet is similar and similarly mounted tomagnet 6 in the distorting device at the sending station. 38 is an ironWire or tape similar to 1, 39 a magnet similar to 3, 41 a permanentmagnet similar to 9, and 40 a telephone receiver connected with magnet39. 37 is a driving cam whose function is similar to that of 8 at thesending station.

The operation of the device is as follows:

The distorting devices at the two stations are started in synchronismand in phase by means of a predetermined signal. The cams may be drivenby clm-kwork, for example, 100 in order to maintain the necessary degreeof synchronism. 'hcn a signal is impressed upon the tape 1 by means ofmagnet 3, it would normally. if magnets 3 and .6 were at restand thetape moving uniformly, require 105 a certain definite time to betransmitted to the mproducing magnet 6. If, however, magnet 6 is inmotion with respect to 3, the time clapsing between the production of asignal at 3 and its reproduction at 6 will be 110 variable. andtherefore the message sent out from the sending antenna 22 will nolonger be an exact copy of the impressed message.

At the receiving station this distorted message is transmitted to thethermionic ele- 115 ments, being amplified in element 26 and transformedinto low frequency form in element 33. It is then impressed upon thereceiving magnet 36, whose motion is similar to that of 6; The distortedmessage is, there- 1 fore, received from the tape 38 in its normal form,due to the relative motion of 36 and 39 and is then picked up by magnet39 and reproduced in undistorted form in the receiver 40.

As stated before, it is essential that the speed of the moving magnet,during that part of its motion in which it is moving in shall not be forthis restriction the motion may be. arbitrary.

While the invention has been described as applied to radiotelephony itwill be obvious to those skilled in the art that it is applicable aswell to either radio or wire systems of telephony, telegraphy or otherforms of communication involving transmission of varying electricalenergy. The inventlon resides not only in the system as a whole but invarious features of the system as pointed out in the appended claims.

What is claimed is:

1. The method of distorting a signal wave form which consists inmodifying the time phase relation of succeeding portions of said signalwave.

2. The method of distorting a signal wave form which consists inalternately increasinfg and decreasing the time phase relation 0succeeding portions of said signal Wave.

3. The method of secret signaling which consists in distorting the timephase relation of succeeding portions of a signal wave, and intranslating said distorted wave into its original undistorted form.

4:. The method of secret signaling which consists in distorting the timephase relation of succeeding portions of a signal wave, modulating acarrier wave in accordance with said distorted Wave, in transmitting,

receiving and detecting the modulated wave, and in restoring thedetected distorted signal Wave to its original. form.

5. A signal transmission system comprising means for producing audiofrequency signaling currents, means for distorting the wave form of saidsignaling currents, means for transmitting and means for receivingenergy varying in accordance with said distorted Wave form, and meansfor deriving from said received energy currents having the wave form ofsaid audio frequency signaling currents.

6. In a system for secret transmission of intelligence, a source adaptedto generate electrical impulses corresponding to a signal to be sent,means practically simultaneously cooperating with said source to alterthe mutual phase relations of such impulses, transmitting and receivingapparatus for said altered signal impulses, means cooperating with saidreceiving apparatus for restoring said mutual phase relations of thealtered impulses received, and a translating device responsive to saidrestored impulses.

7. In combination with a system for the transmission of intelligence, adistorting device having an input circuit and an output circuit, meansfor supplying currents of a given character to said input circuit, andmeans for varying the mutual relations of said circuits, whereby saidoutput circuit is adapted to supply currents of a different character.

8. In combination, a magnetizable record, a magnetic recordmg device,and per1od1- cally acting means for causing an-irregular I relativemotion of said record and said recording device.

9. The combination of a magnetizable member. means for moving saidmember, a I

recording magnet and a reproducing magnet adjacent said member, andperiodically acting means for varying the relative posi-' tions of saidmagnets during operation.

10. The combination of a record element, a recorder for modifying saidelement in accordance with signaling waves, a reproducer in operativerelation to said element, and means for varying the relative positionsof said recorder and reproducer to cause a distorted reproduction ofsaid signaling waves.

11. The combination of a record element, a recording device and areproducer associated therewith, and means for causing motion of saidrecord element both with respect to said recording device and saidreproducer and for periodically changing said motions by the sameamounts. 7

12. A signal transmission system comprising means for producing audiofrequency signaling currents, means for distorting the waveform of saidsignaling currents, means for transmitting and means for receivingenergy varying in accordance with said distorted Wave form, and meansresponsive to said receiving means for restoring the original wave formof said signaling currents.

13. The method of signaling comprising producing signal -waves,distorting said waves, transmitting energy varying in accordance withsaid distorted waves, receiving said energy, and restoring the originalwave form.

14. The method .of signaling comprising producing signal waves,distorting said waves, transmitting energy varying in accordance withsaid distorted wave, receiving said energy, restoring the original waveform, and producing signal indications by the resulting energy.

15. The method of producing a magnetic record by means of a magnetizablemember and a magnet acting thereupon which comprises producingconstantly varying relative motion between said member and said magnet.

16. A signaling system comprising means for producing signal waves,means for distortmg said waves, means for transmitting energy varying inaccordance with said distorted waves, means for receiving said distortedenergy, and means for restoring the original wave form of said receivedenergy.

17. The method of signaling which comprises recording a signal upon arecord, reproducing the signal from the record, and cyclically varyingthe relation between the and means for partly or wholly compensating forsuch distortion.

19. The combination with means for pro-- ducin a high-frequency wavemodulated in accor ance with voice waves, of means for distortingsaidvoice waves, and means for partly or-wholly compensating for-suchdistortion.

20. The combination with means for producing a high frequency wave, asource of voice current waves and a modulator for modulating said highfrequency waves in accordance with said voice current waves,'of meansfor distorting the voice current waves, and means for partly or whollycompensating for such distortion.

21. The method of signaling comprising producing speech waves,distorting said speech waves, transmitting energy varying in accordancewith the distorted speech ing means for producing voice currents,

means for distorting the wave form of said voice currents, means fortransmittingand means for receiving energy varying in accordance withthe distorted voice currents,

and means for deriving from said energy currents having the form of saidvoice currents.

23. A signal transmission system comprising means for producing currentscorre sponding to speech, means for distorting the wave form of saidcurrents, means for transmitting and means for receiving energy varyingin accordance with the distorted wave form, and means for deriving fromsaid received energy currents in their restored wave form correspondingto speech and for reproducing speech from the restored currents.

In witness whereof, I hereunto subscribe my name this 8th day ofSeptember, A. D., 1915.

HAROLD WILLIAM N IOHOLS.

